Debit cards do need a PIN to work, unless we're talking amounts less than 30€ (since 2017, or 2018, it was 20€ from about 2015, when contactless payment was introduced) - and even then you get asked your PIN once every 5 or 6 payments.

Idea that might work, if they need around 100€ to buy pastries - depending on how much babysitting your character does, and how organized they are in their life, it would be believable for them to simply stick the babysitting money in their wallet and carry it around to use when needed.
(I mean, the other options are to deposit it in the bank, which I haven't known any teenagers to do, or to keep it at home, which is just as believable are carrying it around - if they're not likely to get mugged.)